Savel brain dump in English!

My brother presented me old radio tube datasheet book. In his Antique Shop you can find interesting stuff and for electronics hobbyist. Also he gave me very old radio tubes dated 1920…1930 years! With very strange base connectors and heating voltages.

This book was printed in 1958, in Leipzig. I have only the first volume, but all popular tubes are in the first book. The datasheet book (radio valve handbook) is in three language: German, English and Russian.

I like how tube is called in German language: Röhren, I think, I need to pronounce this word like: “Rioren” 🙂 (in Lithuanian transcription)

There are 549 pages in this, half-sized pocket book. Very good quality of the print. But there are errors in this book. Classical error in soviet tube 6Н2П , pinout is printed like western 12AX7, that “screen” contact is connected to the middle of the heater… Also in replacement table (equivalents table) I didn’t see the note, that these tubes are using different heating voltage.

In eBay I bough quite powerful Peltiers (TEC, Thermo-Electric Cooler) unit. According to description it is “TEC cooler – Thermal Enterprises model CP1-12726”.

Specifications:
Model CP1-12726
50mm x 50mm x 3.64mm
245 – 320 Watts of cooling power
Operates from 0-15 volts DC and 0-26 amps
Operates from -60 deg C to +180 deg C
Each device is fully inspected and tested
Fitted with 6-inch insulated leads
Perimeter sealed for moisture protection

I don’t know the efficiency of such device, but let’s hope, that at least 10% from its 200W can be used for cooling.

This unit is about as twice as big as my older TEC unit. For hot side I’ll used big Pentium 4 cooler, and the cold side will be small chamber. Now I need to find quite powerful power supply for this device. I need some PSU with feedback, as I need to adjust temperature.

Recently I found plugin for CadSoft Eagle PCB software. Together with freeware ray-tracing software POV-Ray it produces 3D images of PCB boards. It looks like nice illustrations for PCB assemblage instructions. You can see how your board must look like. Also, you can see proper colors of resistors…

Thermoregulated fan control board.
3D library is not full. So these generated boards are missing of components. In this image, you can see, that one power transistor and trimmer are missing.

Continue reading →

Just few experiments in Mythbusters style. It is funny experiments with short circuits, high currents, flames and fumes. The voltage is lowered, but current is more than 200A.

The test device schematics looks like this: welding transformer with fuse and thermal protection on high voltage side. On lower side are rectifier, capacitor, voltmeter and shunt to measure current. The shunt is too weak for these experiments- the current is more than 200A.

The “schematics” before experiment:

The victim- 4 square mm copper wire with PVC isolation (~AWG 10…12).

This experiment is unfinished, as the copper wire didn’t melted- the automatic fuse box triggered and disconnected mains. This means, that the current in 230V side was much more than 25A for a long time.

Here is short movie of the experiment: XVid, 670kb. With sound. take a note how wires jumps from magnetic flux caused by high current.

Next experiment with thinner wire. It is about 1 square millimeter solid copper wire (AWG 16) with triple insulation. This special insulation is with filler to stop fire.

The wire melted near connector. The short movie of the experiment: XVid, 670kb. Highly recommended to see the movie with sound.

Ant the last experiment in this day. This is standard tape recorder’s mains cable. With power rating printed on the connector: 230V, 2,5A.

Interesting fact, that short time before destruction, this cable managed to pass 70A current…

Movie of the last experiment: XVid, 670kb, sound is mandatory for this movie. You must feel the power of the blast.

System: Windows XP Pro SP2, P4, PCIe system, Radeon X700 with dual output.

Image on single monitor. Please remember the image ratio.

When I move image to the left and the bigger part of the window is in the left monitor.

And I move the windows to the right. As soon, as bigger part of the windows is on right monitor, image jumps. But again, the image is squeezed.

The images are from DScaler, with overlay video. Something same is from media player too.

This web page and lots of other small web pages are powered from recycled computers. The hardware is very old… Yesterday, very old Seagate SCSI disk drive failed… This was very sad news, as the backup of the disk is not created. So all stuff in /home directory was almost lost. When drive was removed from the system and cooled down, the data was recovered. Almost all data. There was lots off abandoned stuff in various hidden directories and few semi finished projects. The data was from old pictures for ebay auction to some heavyweight warezes.

Here is the picture of our RIP, Seagate ST32171W Barracuda hard disk.

According to some label attached to it, it was sold in 1997. This disk started carrier as part of RAID system of some local company. When bigger company acquired that smaller company, the hard disks were stored in some warehouse. After some storage years, the disk was recovered, reformatted and placed in my web server.

Disk didn’t managed to stay alive for ten years… Rest in peace… You think so? No. The drive will be disassembled to various interesting parts. Like grinder, few electronic details and quite powerful magnets.

Don’t forget to create backups of your important data!

PWM transformer are wounded like ordinary transformers. But there are some important differences. As the working frequency of the transformer are much higher than ordinary line transformer, the windings contains much less turns. Also, skin effect is introduced. Also there is some effect with magnetic flux. The simplified description is that the flux tends to stick to core. So all the windings must be as close as possible to core. Engineer must select the core that all the windings fills the core window.

There few simple rules when winding the transformer. Keep highest current winding nearer to center core. Keep all winding interleaved across the bobbin width to optimize coupling with the primary winding.

Example transformer: 4 windings = 5V, 5 windings = 7V, so 4+5 = 12V.

Since so few turns are involved in these outputs, it is usual for multiple parallel wire strands to be used on each output winding, and for the 5 V and 7 V outputs to be constructed as separate windings. This means, that sometimes you need to start even 8 wires at once.

To make coupling between primary and secondary (-ies) better, especially when it is impossible to place all secondaries in one layer, it is possible to split primary.

Np-primary, Na-BIAS.

Red lines in the picture indicates wrapped insulation of Polyester Tape, 3 layers. Ordinary tape sold in local stationer’s (office) shop is not good. The tape must be thermal-proof. Original tape used in transformers can withstand even hot iron touch.

And here is some old manual winding machinery. And one half of primary are already done.